Converging lines of evidence suggest that age-related changes in cognition, and particularly, executive function may exert downstream effects on physical function. However, there is a paucity of data regarding the role of these functions in the natural history of physical disability. We propose to address this gap by building on an established ongoing prospective cohort study of initially high-functioning women, aged 70-80 at baseline, the Women's Health and Aging Study II (WHAS II). Thus, our first aim of this ancillary study is to characterize rates of change in various domains of cognitive function over a 9-year interval. Less clear is whether these changes in cognition predict performance-based changes and self-reported transitions to preclinical difficulty independent of the well-studied mobility pathway. Thus, our second aim will be to test the value of a cognitive pathway to preclinical difficulty and disability in three groups of functional outcomes, categorized according to the putative demands they place on mobility, cognition, or both pathways. Our third set of aims will parallel the WHAS II's innovative efforts to assess preclinical functional difficulty in the mobility pathway by developing more valid and sensitive assessment method to better capture functional changes and compensations in complex activities of daily living typically not reported using standard self-report methods. Our fourth aim seeks to translate these epidemiologic findings into clinical terms by exploring how threshold relationships between cognition and physical function correspond to standard clinical indices of cognitive impairment. The WHAS II offers a unique opportunity to explore in-depth causal pathways between cognition and progression to physical disability for numerous reasons. The majority of women have been retained and evaluated over repeated intervals using state-of-the-art self-report measures comprehensive assessments of mobility, basic, and complex physical functions, and, a uniquely enriched cognitive protocol, developed extensively by the principal investigator. We will synthesize research findings from this study toinform the broader aims of the WHAS II renewal study to develop a conceptual framework that prospectively identifies precursors and major pathways in the natural history of disability. Understanding the roles that cognition may play in the transitions to disability will provide opportunities for better identifying at-risk individuals and developing targeted primary and secondary preventive interventions.